Garth Brooks performed a guest-heavy Nashville concert in celebration of his album sales.

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Fans seldom go to a Garth Brooks show not knowing exactly what to expect. Country’s all-time biggest superstar has been doing multi-night arena residencies and blowing roofs off with full-band hits revues for two years now. But Monday night at Nashville’s Ascend Amphitheater, where the Tennessee Department of Tourism and Development honored the singer for being the first artist to have seven albums go Diamond (meaning each is 10-times Platinum), fans arrived knowing only that Brooks planned on playing seven songs acoustic at the free concert. That seven-song set did happen, as promised. And, as expected, Brooks handily captivated the crowd of 6,800 with nothing more than a headset mic, acoustic guitar and bottomless pit of twinkle-eyed charisma, singing modern American songbook classics like “The Thunder Rolls,” “Unanswered Prayers” and, of course, “Friends in Low Places.”

But what made this a truly once-in-a-lifetime Garth show was an opening star-studded run of Brooks leap-frogging through his catalog with the help of his friends in high places. And we’re not just talking about Tennessee governor Bill Haslam, who presented Brooks with a seven-diamonds-encrusted commemorative belt buckle. But how ’bout Reba opening the show with a honky-tonkin’, sorrows-drowning “Not Counting You,” after regaling the crowd with anecdotes of taking fellow Oklahoman Brooks on tour as an opening act. “I was down in my dressing room getting ready, and my tour manager, Jim Hammond, came up and said, ‘You’re not gonna believe this guy that’s opening the show for you tonight … he’s all over the place!'”

Despite being perhaps the least known of the six guests, Chris Young delivered one of the most memorable vocal performances of the night, out-singing the man of honor on “The River.” And Jason Aldean, easily the most contemporary superstar to show up, turned in a performance of “Much Too Young (To Feel This Damn Old)” that was so obviously heartfelt and expertly delivered that it may have even silenced some detractors that call him soulless. “I kind of feel weird telling you this,” a gushing Aldean told a blushing Brooks, “but I had pictures of you on my wall when I was growing up.”

On the more predictable end, Brooks’ better half Trisha Yearwood joined the singer for a Kodak-moment duet on “In Another’s Eyes” (harmonizing a cappella on the song’s rousing peak) before taking the spotlight to sing a stunning “Walk Away Joe” at Brooks’ request.

But if anyone stole the show, it was Kelly Clarkson, not only bringing the gospel with a sky-scraping, call-and-response-heavy “We Shall Be Free,” but also inspiring the night’s most spontaneous moment. That came when Clarkson voiced her disappointment that fellow surprise guest Steve Wariner, who joined Brooks for a spirited “Longneck Bottle,” didn’t stick around to sing his 1987 hit “The Weekend.” Keeping Clarkson onstage, Brooks called Wariner back out to put him on the spot for “The Weekend.” As hype as Garth crowds get, it seemed no one in the house was as thrilled as Clarkson, who danced and grinded jokingly with Wariner as he tried to concentrate on remembering his own lyrics. “I want you to sing to me, I’m being serenaded,” she joked. And when Wariner got to the line, “If I can’t have you tonight,” Clarkson was quick to interject, “You can, Steve.”

“I wanted to name it ‘Randy Travis’ because it was selling the shit out of everything,” Brooks joked about his 1989 self-titled debut album, before serenading all with a solo version of “The Dance.” That was perhaps a nod to Travis, who was spotted in the crowd shortly before show time and also made an appearance backstage. It was also no joke, in that Brooks – now the first artist in history with seven diamond albums – has sold more than 138 million records in the U.S. alone, making him the Number One solo artist of all-time. As fans once again spent the night singing his songs back to him, it was no wonder why.